How to raise shed off concrete slab?

[Ali81]

I have a large old 24' by 24' concrete slab in my garden that I'm building a 14' by 11' shed on

First time I've made a shed and I didn't really consider how to protect the PT bottom plate from water or how to stop water getting under the frame.

Will raising it on to 1 course of 65mm high bricks be enough, or do I need 2 courses? I can put sill sealer under the bottom plate once raised

My shed is pretty much as high as I'm permitted to build it, so want to raise it the least. The roof overhangs 30 cm on sides, 45 cm on front, and finished shed will be wrapped, batton and feather edge clad

 

[Notch7]

raising it by 1 brick will certainly help protect the structure -if you use breather membrane, put timber battens vertically onto your OSB, then clad, that will make the walls weathertight and you could make the brickwork flush with the frame work then run the cladding just a bit over the brick to stop rain ingress

the issue remaining is stopping water running under the brick and onto the shed floor -thats a bit more tricky

 

[Ali81]

Thanks. I could mortar the bricks and seal them on the outside to help stop water sealing through?

Would I normally brick all the way around including under the doors creating a step, or leave the door sections free of bricks and address the water issue at the doors after?

 

[Murdochcat]

I'd be leaving air gaps around the base ............

 

[Tigercubrider]

Might be easier to buy some concrete / composite fence posts and lay them widthways?
You could then use DPC material between the posts and timber.
Leave a gap for airflow, ideally a French drain and then use mesh to stop rats etc.

 

[Ali81]

I plan to keep the concrete base as the shed floor. And don't plan to insulate it. Do I need much of an air gap between the frame and bricks?

 

[Ali81]

Here's the shed so far - used some of the material from the big 24' x 24' I took down which covered the whole concert base

 

[opps]

Why not use plastic shims to raise it by 6+mm?

Then squirt expanding foam into the gap from the outside. The excess inside the shed can be carved away.

PV foam will hold back rain/standing water.

I have used it in the past for such purposes. It works well but it will turn orange and brittle in direct sunlight. That said, in the scenario described, the UV light will probably only penetrate about 4mm deep. The rest under the timber frame will be fine.

 

[Ali81]

Why not use plastic shims to raise it by 6+mm?

Then squirt expanding foam into the gap from the outside. The excess inside the shed can be carved away.

PV foam will hold back rain/standing water.

I have used it in the past for such purposes. It works well but it will turn orange and brittle in direct sunlight. That said, in the scenario described, the UV light will probably only penetrate about 4mm deep. The rest under the timber frame will be fine.

As the concrete slab is not very level I've put temporary wood shims of different sizes around the whole thing, and I can change these to bigger plastic ones easily.

I'd like to do something else with the concrete slab outside the shed, like a seating area with gravel and paving, which would be higher than the bottom plate of the shed, so lifting it up higher like 70 mm + might be a good idea.